<!DOCTYPE html>	 
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" lang="en">
    <head>
        <title>Test</title>
    </head>
    <!-- ERROR: the prefix 'my' is not declared -->
    <body epub:type="bodymatter my:property">
        <h1>Test</h1>
    </body>
</html>